Soybean rust trackers gear up for season

Soybean stocks worldwide have declined to near record levels and the subsequent increase in prices has spurred many growers to add beans to their cropping list or to increase acreage.

In the Southeast most of that acreage will likely come on the heels of a big wheat crop, possible up by as much as 25 percent from the 2006/2007 crop. Unfortunately, many of the double-crop beans will likely be planted later than optimal, exposing them to a more severe threat from soybean rust.

Though rust has been a dire possibility for Southeastern soybean growers since it first arrived from South America, it is yet to make it to the Carolinas and Virginia in time to do significant damage. Early arriving rust and late planted beans could be a bad combination for soybean growers in the Southeast.

If nothing else Asian soybean rust, caused by Phakospora pachyrizi, is unpredictable. “We just don't have enough years of data to make an accurate model as to when it will get to one state or another,” says long-time rust tracker John Mueller. Mueller adds that where rust spores over-wintered has not been a good indicator of where the disease will occur the following summer.

In 2007 Asian soybean rust was found in 336 counties in 19 states in the continental U.S. as well as Hawaii, Canada and Mexico. This is the most widespread distribution of this disease since it was first discovered in the U.S. in 2004.

In the winter of 2007, soybean rust disease spores were found as far north as Montgomery, Ala. on kudzu. Despite some predictions that this would propel the disease into soybean production areas earlier than in previous years, this did not happen.

Severe drought in Alabama and Georgia kept the disease bottled up for most of the 2007 growing season. Though some soybean fields were sprayed in South Carolina to prevent rust, only one spray was required and in most areas of the state no fungicide was used.

In North Carolina, long-time Soybean Specialist Jim Dunphy says they are not taking any chances with soybean rust. Soybean acreage could push 1.5 million acres in the Tar Heel state in 2008 and high prices could make it the most valuable agricultural crop in North Carolina.

He points out that Florida has rust on kudzu in south Florida (Tampa and below), and in the Jacksonville area. They have had rust on kudzu in the Panhandle until the past two weeks.

In Georgia and Alabama, typically key indicator states for rust movement into the upper Southeast, some soybeans are planted, but no rust is reported. Alabama has reported rust on kudzu.

Warm, dry weather allowed growers near the Gulf Coast in Alabama to plant full season soybeans in mid-March. Most of the full season beans in the Southeast will be planted in April, giving researchers ample time to get sentinel plots planted and growing.

Last year the most rapid movement of soybean rust came from Louisiana and Mississippi. Rust movement northward from the Delta was spurred by plenty of moisture and high winds provided by a series of tropical storms. Rust made its way into the high soybean producing areas of the Midwest.

Though moving farther north and into Illinois and other soybean producing states for the first time during a growing season, the disease still arrived too late to cause any widespread damage.

In 2008, Mississippi had 20 sentinel plots planted by the end of March and Louisiana had just begun planting their sentinel plots of soybeans.

In Texas, continued wet weather has spurred the early greening up of kudzu, but so far no rust has been detected.

Soybean growers in the Southeast are fortunate to have a loose-knit, but very well connected network of scientists monitoring the movements of soybean rust.

When rust was first acknowledged as a possible threat to Southeastern soybeans in 2004, researchers from Virginia Tech, North Carolina State, Clemson, Georgia, Auburn and Florida banded together and came up with a plan to put in sentinel plots of soybeans to monitor the disease. In addition, county agents have become involved in the project.

The end result may not be button-down scientific, but it is one of America's top success stories in agriculture. Essentially these researchers have built a fence around the Southeastern soybean crop — state by state. As the disease moves northward, researchers track it mile by mile, providing farmers plenty of time to treat endangered beans with fungicides.

Fortunately, soybean rust is a relatively easy fungus to control. Both triazole and strobilurin fungicides do a good job or either preventing (strobilurins) or stopping infections.

Though South Carolina's Mueller stops short of his one-time referral of rust as a ‘wimpy little fungus,’ he says there are a number of highly effective fungicides available to manage the disease.

The 2008 crop will benefit from several years of experience which has fine-tuned the sentinel system to the point that virtually all soybean growers in any Southeastern state know within 24 hours when soybean rust is spotted within 100 miles of their farms.

Not only do growers know when TO spray, they also know when NOT to spray, says Mueller. Despite recently taking over as Interim Director of Clemson's Edisto Research and Education Center, Mueller will again spearhead South Carolina's soybean rust tracking efforts.

Due in large part of Mueller's efforts in developing a communication link with growers, the amount of fungicide sprayed on soybeans in South Carolina has been decreased since the rust scare first surfaced in 2004.

Jim Dunphy and Steve Koenning at North Carolina State have likewise developed a loyal following, via a rust update that in high risk times is done almost daily. Both Dunphy, the state soybean specialist and Koenning, a plant pathologist, have done an excellent job of keeping North Carolina growers well ahead of rust.

In Virginia, David Holshouser also produces an electronic soybean production newsletter, which includes information to keep growers aware of rust movement. Virginia is expecting a significant increase in wheat acreage and subsequently in double-crop soybeans.

Though none of these scientists intended to be an Asian soybean rust specialist, they along with colleagues at the University of Georgia, Auburn University and the University of Florida have developed into a formidable team. Collectively, they are gearing up for another season in hopes of helping growers avoid damage to what looks like the most valuable soybean crop in years in the Southeast.